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Thread: Pre-Cat And Wrap

  
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    Pre-Cat And Wrap

    Is it worth wrapping the pre-cat to keep engine temps down before putting it on?

    I have some spare mani wrap laying about.

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    It's not worth wrapping any part of the exhaust

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    right ok thanks for the quick reply

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    Don't know what engine you have Lee, but the factory precat on my Zlet has heat insulation over the vast majority of it so there must be some point to it IMO.

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    I think he means the pre cat replacement pipe... I was thinking about doing the same.....

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    yeah the pre cat replacement pipe, and its a coupe turbo

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    The OE pre-cat as the heat shield round it to retain heat to make it heat up quicker to start working. The insulation isn't there to reduce under bonnet temps.

    So when you replace the precat, then the insulation isn't needed, and wrapping parts of (tubular) manifold/front pipe has been proved to make them fall apart by retaining too much heat for too long a period, and altering the dendritic structure of the metal.

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    lee gsi's Avatar
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    Really?

    I had my XE engined 4 branch wrapped for 4 years with no problems.

    The stuff worked so well the heat sheild used to be hotter then the manifold.

    Also you will find most race car teams will wrap exhausts too (Allthough they dont car how long the last for)

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    Likewise, I have wrapped manifolds and downpip[es before with no ill effects.
    Another thing to consider is the risk of fire if you park your car over grass,such as at shows etc.When cats first appeared on mainstream cars there were many cases of vehicles being burnt out because the heat from the cat would be enough to ignite the grass underneath if it was long/dry enough.IIRC some manufacturers were sued for not safeguarding against this happening.Remedy? Insulation.

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    lol. The old chestnut -"I did it and nothing happened" is the same as saying I smoke and I haven't got cancer

    As said above wrapping the manifold or down pipe will trap heat in the pipe and make it run consistently hotter than if was left unwrapped, plus it will retain that heat longer and cool down much more gradually once the engine is switched off. This will weaken the metal. And AFAIK no exhaust manufacturer will honour any warranty claim where the zorst has been wrapped.

    Most (wise) race teams have now ditched wrapping and use ceramic coatings on the exhaust to keep it hotter and insulate other engine parts (oil lines, fuel pipes etc) from ambient heat. Doing this lets thew pipe cool down naturally, and it doing so they don't have to replace them no where near as often as they did when they were wrapping them.

    As for the fire risk - I think you'll find that heat shields are fitted where needed, and the pipe remains uninsulated. Heat shields deflect/reflect heat rather than contain it.

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